Cup-shaped photoconductor tube



Oct. 29, 1968 c. c. CASAMO ET AL CUP- SHAPED PHOTOCONDUCTOR TUBEOriginal Filed March 4, 1965 HYDKATED F/RE ENVELOPE, sup/ 0 STRUCTURE AAND PHOTO-CONDUCTOR awn/r //v 271?) AND m/mr Amos/w mm D:-

M05F/VERE [Tm mar mm OPE AND SUPPORT sm/c- TUAE W/7l/ PAOTU-CWNDUCf/VEEZEMENT THEEEEE TWEEN w pm AND war 47- AVE? 7 AT MOSF/lE/if I ANDSUPPORT 57406 Tl/AE T 0 SEAL AND ENC! 051? P1407 O-CONDl/CTOK ELEMENT THEREBE 7' WEE/V //V DRY AND /NE/? T ATMOSPHERE l REMOVE SEALED ENVELOPEAND 5UP- FORT STFUC T (/35 CW/VTA/Nl/VG PHOTO- CONDUCTOR EZEMENT FROMDRY AND Fig- 5 INVENTORS CHARLES C. CASAMO Down: 2?. K575767751?ATTORNEY r from the light-frequency United States Patent 3,408,522CUP-SHAPED PHOTOCONDUCTOR TUBE Charles C. Casamo and Donald R.Kerstetter, Emporium,

Pa., assignors to Sylvania Electric Products Inc., a corporation ofDelaware Original application Mar. 4, 1963, Ser. No. 262,650, now

Patent No. 3,326,618, dated June 20, 1967. Divided and this applicationJan. 24, 1967, Ser. No. 611,307

3 Claims. (Cl. 313102) ABSTRACT OF THE DISCLOSURE Cross-references torelated applications This application is a division entitledPhoto-Conductor Mar. 4, 1963, US. Ser. Casamo et al.

of a parent application Device and Process, filed No. 262,650, forCharles C.

Background of the invention Known photoconductor tubes generally consistessentially of a light-frequency responsive element hermeticallyenclosed intermediate and within a glass bulb and a supportingstructure. The glass supporting structure usually supports thelight-frequency responsive element and a pair of conductors areconnected thereto. Additionally, the conductors are formed to extendthrough the glass supporting structure to permit electrical contact withan external supply.

Further, the glass supporting structure usually has an exhaust tubeextending therefrom which, after the glass bulb has been sealed to thestructure, permits evacuation of the atmosphere surrounding thelight-frequency responsive element and replacement thereof with a dryand inert atmosphere. Moreover, the bulb which is sealed to the glasssupporting structure is transparent or at least partially so and alignedwith the light-frequency responsive element to permit light energizationof the element.

In one process for manufacturing photoconductor tubes, theabove-mentioned glass envelope and glass supporting structure arebrought to in sufiicient amount to cause the formation of a seal.Following, the atmosphere intermediate the glass bulb and glasssupporting structure is evacuated and replaced with a dry and inertatmosphere.

Although the type of structure and processing is commonly used inphotoconductor tube manufacture, it has been found that the heatrequired to formulate the seal is diflicult to confine within the sealarea. Further, the amount of heat permitted for the sealing process iscritical because of the deleterious elfects of excess heat on thelight-frequency response element. Additionally, the sealing of glass isa slow and costly operation and a glass supporting structure does notsatisfactorily conduct heat away responsive element. Moreover, thereplacement of the atmosphere surrounding the lightfrequency responsiveelement is unwieldly and requires into contact and heat appliedthereexpensive equipment. Furthermore,

Objects and summary of the invention It is an object of this inventionto enhance the operating temperature of a photoconductor tube.

A further object of this invention is to improve the heat dissipatingcharacteristics of a photoconductor tube structure.

A still further object of this invention is to improve the hermeticsealing of a photoconductor tube whereby the lightrequency responseelement thereof is not deteriorated during the manufacturing process.

Another object of this invention is to provide a process forphotoconductor tube manufacture which does not require expensiveevacuation equipment.

Still another object of this invention is to simplify the photoconductortube manufacturing process.

And yet another object of this invention is to enhance the rigidity andruggedness of a photoconductor tube structure.

Briefly, these objects are fulfilled in one aspect of the invention bythe provision of a photoconductor tube construction having a metalsupporting structure and a lightfrequency responsive element attachedthereto. Further, a light-frequency transparent envelope is sealed tothe metal supporting structure forming an enclosure therebetween whereinthe light-frequency responsive element is contained. In thephotoconductor tube manufacturing process, the envelope and a supportingstructure having an atfixed response element are dehydrated in a dry andinert atmosphere. Subsequently, the envelope and support structure arecontacted and a seal is made therebetween. Thus, the light-frequencyresponsive element is enclosed and hermetically sealed in a dry andinert atmosphere.

For a better understanding of the present invention, together with otherand further objects, advantages, and capabilities thereof, reference ismade to the following disclosure and appended claims in conjunction withthe attached drawing.

Brief description of the drawing FIG. 1 is an elevated view of aphotoconductor tube; and

FIG. 2 is a block diagram illustrating the process for making thephotoconductor tube.

Description of the preferred embodiment Referring to FIG. 1 of thedrawings, there is illustrated a photoconductor tube having a cup-shapedsupport structure 3 with a flared skirt portion 4 at the open endthereof. The structure 3 is formed from metal or a metal alloy such as anickel-chrome-iron alloy, which has a desired heat dissipatingcharacteristic and an atfinity to the formation of a hermetic seal.Further, the cup-shaped configuration acts as a heat sink wherein excessprocessing and operating heat is absorbed. Additionally, the flaredskirt portion 4 provides a radiating surface whereby absorbed heat isremoved from the structure 3.

Afiixed to and supported by the support structure 3 is a light-frequencyresponse element 5. The response element 5 may be any of the numerouslight-frequency response materials and is aflixed to support structure 3by a hold down connector 7 and a conductor 11. The hold down connector 7electrically and mechanically interconnects the response element 5 andthe support structure 3. Further, the conductor 11 is formed to provideelectrical and mechanical attachment to response element 5 and isinsulatingly but mechanically attached to support structure 3 by meansof a glass bead 13 imbedded therein. Additionally, the conductor 11extends from support structure 3 for electrical connection to anexternal supply. Moreover, a conductor 9 is formed to extend from and isattached to the support structure 3 to provide electrical connectionfrom the response element 5 through the hold down connector 7 andsupport structure 3 to an external supply.

A light-frequency transparent envelope 17 which may be of ceramic,plastic, and numerous other materials but preferably of glass, ishermetically sealed to the support structure 3 at the jointure position19. Thus, the envelope 17 and support structure 5 form a sealedenclosure 21 wherein is contained the light-frequency response element5.

In the process of making photoconductor devices, as illustrated in FIG.2, the envelopes and supporting structures with the light-frequencyresponse elements afiixed thereto, are fired in a dry and inertatmosphere. The firing time as well as the atmosphere temperature isadjusted to cause the complete dehydration of the envelopes and thecombined supporting structures and response elements.

As is well known, the dehydrating temperature of the envelopes usuallydiffers from the dehydrating temperature of the supporting structuresand afiixed response elements. Thus, separate atmosphere temperatures oralternately separate furnaces are preferable for the firing ordehydration process.

Following, an envelope is placed in contact with a supporting structurewithout exposing either element to other than a dry and inertatmosphere. Further, the area of contact between the envelope andsupport structure provides a jointure adapted to the formation of a sealtherebetween. Additionally, the envelope may be, if desired, but notnecessarily need be placed in contact with the response element toprovide a heat conductive path for the removal of heat therefrom.Moreover, when the envelope and response element are touching, thevolume of atmosphere entrapped intermediate the envelope and supportingstructure is reduced.

Subsequently, sufficient heat is directed on the jointure or contactingenvelope and support structure area to cause a seal therebetween,whereupon the response element is hermetically enclosed in a dry andinert atmosphere. The heat, sufficient to provide a seal, may besupplied in any of a number of ways, and one preferred method is to useRF heat radiated from an appropriately postioned RF coil. Further,during the actual process of seal formation, a blast of dry and inertatmosphere may be directed into and striking the closed end of thecup-shaped support structure to provide additional cooling for theresponse element affixed thereto. After sealing the device is removedfrom the furnace in completed condition.

As a specific illustration of the process, a cadmiumsulfide wafer wasaflixed to a nickel-chrome-iron alloy supporting structure. Thisparticular alloy consists essentially of 42 percent nickel, 4-8 percentchrome, and the balance substantially iron. The supporting structure andresponse element were placed in a furnace having a dry nitrogenatmosphere flowing therethrough which was maintained at a temperature inthe range of 125 C. to 225 C. and preferably at about 175 C. wherein thesupport structure and response element remained until completelydehydrated.

At substantially the same time a lead glass envelope, designated as 0120glass by the Corning Glass Works of Corning, N.Y., was placed in afurnace having about the same dry nitrogen atmosphere flowingtherethrough. This atmosphere was maintained at a temperature in therange of 350 C. to 450 C. and preferably about 400 C. until the envelopewas completely dehydrated.

Upon dehydration of the glass envelope, the metal sup porting structure,and the affixed response element, the envelope was transferred throughan interconnecting tube containing a dry nitrogen atmosphere and broughtinto contact with the supporting structure. Further, the contactingsurfaces formed a jointure for the sealing thereof and the responseelement was enclosed between the envelope and the supporting structure.

Following, the jointure was encircled by an RF coil and radiated RF heatwas applied thereto. At the same time pressure was exerted on theenvelope to provide an intimate relationship at the envelope-supportingstructure jointure thereby enhancing the sealing process. Further, theenvelope was forced into contact with the response element to provide apath for the conduction of heat therefrom. Moreover, the volume ofatmosphere entrapped intermediate the envelope and support structure wasreduced.

Upon completion of the seal, the RF heat was discontinued, the pressureexerted on the envelope withdrawn, and the cooling blast interruptedThereupon, the encircling RF coil was removed from around the jointureand the completed device discharged from the furnace.

Thus, there has been provided a structure and a manufacturing processwhich is unique and possesses a host of advantages over prior structuresand processes. The improved metal supporting structure acts as a heatsink? for the conductions of heat from the response element not onlyduring manufacture but during operational use as well. Further, the needfor critical control of temperature during the sealing process andduring application of the device is substantially reduced. Moreover, theheat conductive path provided by contact between the envelope andresponse element as well as the cooling blast of dry and inertatmosphere permit the use of an increased amount of heat for the sealingprocess. Additionally, the use of RF heat enhances the sealing processand reduces the period required for seal formation. Furthermore, theprovision of a photoconductive device sealed in a dry and inertatmosphere without first requiring evacuation permits the use ofinexpensive manufacturing equipment and is adapted to automatedtechniques.

While there has been shown and described what is at present consideredthe preferred embodiment of the invention, it will be obvious to thoseskilled in the art that various changes and modifications may be madetherein without departing from the invention as defined by the appendedclaims.

What is claimed is:

1. A photoconductor type tube comprising:

a cup-shaped metallic supporting structure having a flat base and asubstantially cylindrical stem terminating in a flange;

a light frequency responsive element supported by and electricallyconnected to said supporting structure;

a light-frequency transparent envelope aligned with said light-frequencyresponsive element and sealed to said supporting structure to provide anenclosure containing said responsive element said envelope beingcup-shaped with a stem having the edge thereof sealed to said flange toform said enclosure between said stems, said light responsive elementbeing sandwiched between the bases of said support structure andenvelope;

a dry and inert atmosphere within said enclosure; and

a pair of conductors electrically connected repectively to said metallicsupporting structure and to said reresponsive element and extendingexternal to said enclosure.

2. The photoconductor tube of claim 1 wherein a holddown strapelectrically and mechanically interconnects said light-frequencyresponsive element and said metallic supporting structure and one ofsaid conductors is electrically and mechanically attached to saidmetallic supporting structure and extends outwardly therefrom.

3. The photoconductor tube of claim 4 wherein the other of said pair ofconductors is electrically connected to said light-frequency responsiveelement and insulatinging structure.

6 9/1948 Cashman 3131-102 X 1/1956 Cashman 313102 X FOREIGN PATENTS 3/1960 France. 4/ 1960 France. 4/ 1962 France.

ROBERT SEGAL, Primary Examiner.

